I see this is due to preconditioner, but could you explain shortly what particularly causes this problem? It's not obvious to me.
Thanks. On 09.01.2012 17:36, Matthew Knepley wrote: > On Mon, Jan 9, 2012 at 10:31 AM, Alexander Grayver > <agrayver at gfz-potsdam.de <mailto:agrayver at gfz-potsdam.de>> wrote: > > I have tested default GMRES+ILU(0) solver for problem of size > ~200000 and I observed that both convergence rate and accuracy > degrade when I increase number of processes. > E.g., number of iterations almost doubles when going from 1 to 4 > processors. > > I noticed that ILU(0) is somehow represented by sequential > matrices internally and feel that this might be a reason? > > > The default is Block Jacobi+ILU(0) and GMRES(30) which will definitely > degrade as the number of > processes is increased. You would need to use an optimal > preconditioner like Multigrid if you want > a constant number of iterates. > > Matt > > Regards, > Alexander > > > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which > their experiments lead. > -- Norbert Wiener -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120109/4c917941/attachment.htm>
